in debug mode it shows only "No Chunk" Messages and does not work as expected.

May because a play the "crash-site" scenario with red-mew-surface?!

I'm not so sure what you mean but the mod only activates itself on surface indexed by 1 which by default is nauvis. There currently is no way to activate it for other surfaces as most other surfaces that existed, at the time I made this mod, were not meant to have trees or tree growth (space ship, factory buildings, underground, space, etc.).

I could possibly make a setting that would allow you to specify which surfaces to activate this mod on but might take me a couple days as I'm currently very busy.

wow .. thanks for the fast response.. and the hint with surface 1... i setted it to 2 by myself and its all good and running :-)

Awesome, I will probably still add a setting just in case others have different or multiple surfaces they want the trees to spread on (most of the code is actually ready to support multiple surfaces in a performant way but I just haven't added a way to add more yet).